The 83-year-old Rothschild Mansion on the Upper East Side was snapped up yesterday by a steel magnate for $25 million, sources told The Post.

Buyer Leroy Schecter, 85, who owns Marino/Ware Industries, is planning a multimillion-dollar overhaul of the historic property so he can turn it into a single-family home, sources said.

The 11,256-square-foot estate — at 41 E. 70th St, between Park and Madison avenues — had been on the market since 2004, and was sold by its last tenant, the nonprofit think tank Century Foundation.

At 28-feet wide, the mansion — built by Baron Walter Rothschild, from the British banking family — is grander and roomier than the standard 20-to-25-foot-wide town houses in the neighborhood.

It currently has offices, including a second-floor boardroom, although the original first-floor kitchen and second-floor library are still intact. It could hold up to six bedrooms.

The six-story home also comes with a gorgeous 33-foot garden with ginko trees — part of a former communal garden that was once shared by members of the Lehman banking family, who owned several nearby mansions.

It also has a terrace on the sixth floor with striking views of the city, including the Four Seasons Hotel.

There is also room to add another garden on the roof.

The entryway to the town house includes a sweeping, curved staircase topped by a skylight that has been covered for decades.

“That’s just one of the things that will need to be restored during the renovation,” said a source.

Schecter — who tried to hide his identity in the sale by buying under an LLC — also has two joined apartments at 15 Central Park West for sale as a combo for a whopping $95 million.

Brown Harris Stevens broker Paula Del Nunzio had the listing for the Rothschild home, which Woody Allen once considered buying.

The Century Foundation has used the town house as headquarters since 1958, and the sale couldn’t be finalized until it found new offices.

The group will move to a 15th-floor rental on Whitehall Street in the Financial District, foundation spokesman Derek Newton said.

The town house’s price has fluctuated over the years; in 2007, it was on the market for $35 million.